The GNU General Public License

The GNU General Public License is often called the GNU GPL for short;
it is used by most GNU programs, and by more than half of all free
software packages. The latest version is version 3.

The GNU General Public License is available in these formats:
HTML,
plain text,
ODF,
Docbook,
Texinfo, and
LaTeX.
These documents are not formatted for standalone publishing, and
are intended to be included in another document.

The GNU Lesser General Public License

The GNU Lesser General Public License is used by a few (not by any means
all) GNU libraries. The latest version is version 3.

The GNU Lesser General Public License text is available in
these formats:
HTML,
plain text,
Docbook, and
Texinfo.
These documents are not formatted for standalone publishing, and
are intended to be included in another document.

The GNU Affero General Public License

The GNU Affero General Public License is based on the GNU GPL, but has an
additional term to allow users who interact with the licensed software over
a network to receive the source for that program. We recommend that people
consider using the GNU AGPL for any software which will commonly be run
over a network. The latest version is version 3.

The GNU Affero General Public License text is available in
these formats:
HTML,
plain text,
Docbook,
Texinfo, and
LaTeX.
These documents are not formatted for standalone publishing, and
are intended to be included in another document.

The GNU Free Documentation License

The GNU Free Documentation License is a form of copyleft intended
for use on a manual, textbook or other document to assure everyone
the effective freedom to copy and redistribute it, with or without
modifications, either commercially or non-commercially. The latest version
is 1.3.

The GNU Free Documentation License text is available in these formats:
HTML,
plain text,
Docbook,
Texinfo, and
LaTeX.
These documents are not formatted for standalone publishing, and
are intended to be included in another document.

Exceptions to GNU Licenses

Some GNU programs have additional permissions or special exceptions
to specific terms in one of the main licenses. Since some of those
are commonly used or inspire a lot of questions on their own, we've
started collecting them on
our exceptions page.

License URLs

When linking to our licenses, it's usually best to link to the latest
version; hence the standard URLs such as
http://www.gnu.org/licenses/gpl.html have no version number.
Occasionally, however, you may want to link to a specific version of a
given license. In those situations, you can use the following links
[skip links]:

Stable links to each license's alternative
formats are available on its respective page. Not every version of
every license is available in every format. If you need one that is
missing, please email us.

Unofficial Translations

Legally speaking, the original (English) version of the licenses is what
specifies the actual distribution terms for GNU programs and others that
use them. But to help people better understand the licenses, we give
permission to publish translations into other languages provided that
they follow our regulations for unofficial translations:

Verbatim Copying and Distribution

The standard copyright terms for GNU web pages is now the Creative
Commons Attribution-NoDerivs 3.0 United States License. It used to
be (and for a few pages still is): Verbatim
copying and distribution of this entire article are permitted worldwide,
without royalty, in any medium, provided this notice is
preserved. Please note the following commentary about this
“verbatim license” by Eben Moglen:

“Our intention in using the phrase ‘verbatim copying in
any medium’ is not to require retention of page headings and
footers or other formatting features. Retention of weblinks in both
hyperlinked and non-hyperlinked media (as notes or some other form of
printed URL in non-HTML media) is required”.

List of Free Software Licenses

If you are contemplating writing a new license, please contact the
FSF by writing to <licensing@fsf.org>. The
proliferation of different free software licenses means increased work
for users in understanding the licenses; we may be able to help you
find an existing Free Software license that meets your needs.

If that isn't possible, if you really need a new license, with our
help you can ensure that the license really is a Free Software license
and avoid various practical problems.

What Is Copyleft?

Copyleft is a general
method for making a program free
software and requiring all modified and extended versions of the
program to be free software as well.

The simplest way to make a program free is to put it in the
public
domain, uncopyrighted. This allows people to share the program
and their improvements, if they are so minded. But it also allows
uncooperative people to convert the program into
proprietary
software. They can make changes, many or few, and distribute the
result as a proprietary product. People who receive the program in
that modified form do not have the freedom that the original author
gave them; the middleman has stripped it away.

In the GNU project, our aim is
to give all users the freedom to redistribute and change GNU
software. If middlemen could strip off the freedom, we might have
many users, but those users would not have freedom. So instead of
putting GNU software in the public domain, we “copyleft”
it. Copyleft says that anyone who redistributes the software, with or
without changes, must pass along the freedom to further copy and
change it. Copyleft guarantees that every user has freedom.

Copyleft also provides an
incentive
for other programmers to add to free software.
Important free programs such as the GNU C++ compiler exist
only because of this.

Copyleft also helps programmers who want to contribute
improvements to
free software get permission to
do that. These programmers often work for companies or universities
that would do almost anything to get more money. A programmer may
want to contribute her changes to the community, but her employer may
want to turn the changes into a proprietary software product.

When we explain to the employer that it is illegal to distribute the
improved version except as free software, the employer usually decides
to release it as free software rather than throw it away.

To copyleft a program, we first state that it is copyrighted; then
we add distribution terms, which are a legal instrument that gives
everyone the rights to use, modify, and redistribute the program's
code or any program derived from it but only if the
distribution terms are unchanged. Thus, the code and the freedoms
become legally inseparable.

Proprietary software developers use copyright to take away the users'
freedom; we use copyright to guarantee their freedom. That's why we
reverse the name, changing “copyright” into
“copyleft”.

Copyleft is a general concept; there are many ways to fill in the
details. In the GNU Project, the specific distribution terms that we
use are contained in the GNU General Public License, the GNU Lesser
General Public License and the GNU Free Documentation License.

The appropriate license is included in many manuals and in each GNU
source code distribution.

The GNU GPL is designed so that you can easily apply it to your own
program if you are the copyright holder. You don't have to modify the
GNU GPL to do this, just add notices to your program which refer
properly to the GNU GPL. Please note that you must use the
entire text of the GPL, if you use it. It is an integral whole, and
partial copies are not permitted. (Likewise for the LGPL, AGPL, and FDL.)

Using the same distribution terms for many different programs makes it
easy to copy code between various different programs. Since they all
have the same distribution terms, there is no need to think about
whether the terms are compatible. The Lesser GPL includes a
provision that lets you alter the distribution terms to the ordinary
GPL, so that you can copy code into another program covered by the GPL.